Conduction-band offset determination in GaAs-AlxGa1-xAs through measurement of infrared internal photoemission

Internal photoemission from a two-dimensional electron gas formed at GaAs-AlxGa1-xAs selectively doped heterojunctions has been measured for x=0.25, 0.28, 0.36, and 0.38. The photoresponse increases rapidly with the angle of incidence of the light, indicating that it results from intersubbandlike transitions. We have developed a model for the photoemission, and used the measurement to determine the conduction-band offset. We find values of Qe=Ec EG of 0.79, 0.76, 0.67, and 0.65, respectively, for the x numbers stated above, showing a smooth decrease with x.